#!/usr/bin/env python
# -*- coding: utf-8 -*-
# @Time    : 2020/7/28 11:05
# @USER    : Shengji He
# @File    : EditDistance.py
# @Software: PyCharm
# @Version  : Python-
# @TASK:

class Solution:
    def minDistance(self, word1: str, word2: str) -> int:
        """
        Given two words word1 and word2, find the minimum number of operations required to convert word1 to word2.

        You have the following 3 operations permitted on a word:
            - Insert a character
            - Delete a character
            - Replace a character
        Example 1:
            Input: word1 = "horse", word2 = "ros"

            Output: 3

            Explanation:
                horse -> rorse (replace 'h' with 'r')

                rorse -> rose (remove 'r')

                rose -> ros (remove 'e')
        Example 2:
            Input: word1 = "intention", word2 = "execution"

            Output: 5

            Explanation:
                intention -> inention (remove 't')

                inention -> enention (replace 'i' with 'e')

                enention -> exention (replace 'n' with 'x')

                exention -> exection (replace 'n' with 'c')

                exection -> execution (insert 'u')

        :param word1:
        :param word2:
        :return:
        """
        n = len(word1)
        m = len(word2)
        if n * m == 0:
            return n + m
        dp = [[0] * (m + 1) for _ in range(n + 1)]
        for i in range(n + 1):
            dp[i][0] = i
        for j in range(m + 1):
            dp[0][j] = j

        for i in range(1, n + 1):
            for j in range(1, m + 1):
                left = dp[i - 1][j] + 1
                down = dp[i][j - 1] + 1
                left_down = dp[i - 1][j - 1]
                if word1[i - 1] != word2[j - 1]:
                    left_down += 1
                dp[i][j] = min(left_down, left, down)

        return dp[n][m]


if __name__ == '__main__':
    S = Solution()
    word1, word2 = 'intention', 'execution'
    # word1, word2 = 'horse', 'ros'
    print(S.minDistance(word1, word2))
    print('done')
